Anomalous Damping of a Low Frequency Vibrating Wire in Superfluid 3He-B due to Vortex Shielding

Abstract

We have investigated the behaviour of a large vibrating wire resonator in the B-phase of superfluid 3 He at zero pressure and at temperatures below 200 µK. The vibrating wire has a low resonant frequency of around 60 Hz. At low velocities the motion of the wire is impeded by its intrinsic (vacuum) damping and by the scattering of thermal quasiparticle excitations. At higher velocities we would normally expect the motion to be further damped by the creation of quasiparticles from pair-breaking. However, for a range of temperatures, as we increase the driving force we observe a sudden decrease in the damping of the wire. This results from a reduction in the thermal damping arising from the presence of quantum vortex lines generated by the wire. These vortex lines Andreev-reflect low energy excitations and thus partially shield the wire from incident thermal quasiparticles.

Real-time detection of hydrogen absorption and desorption in metallic palladium using vibrating wire method

“…In condensed matter physics, the VW has often been used to study the quantum nature of liquid helium because it can probe the viscosity of a medium surrounding the wire. [22][23][24] In this Letter, we report the first experimental observation of H absorption and desorption processes in metal using the VW technique. The real-time response under exposure to H 2 gas shows that the VW sensor traces the resonance frequency shift with high sensitivity, demonstrating the validity of this technique.…”